It is common practice to chlorinate large bodies of water such as those used in swimming pools and spas to reduce the occurrence and growth of micro-organisms. There are a number of problems encountered by the addition of quantities of chlorine or chlorine-containing compounds to a body of water at regular intervals in order to maintain the required chlorine concentration. One solution to these problems is the use of electrolysis to chlorinate the water. Electrolysis requires salinating the pool water to between 0.2% and 0.8% by weight of sodium chloride and then passing the salinated water through an electrolytic cell that has spaced electrodes coupled to a source of d.c. voltage. The current flowing between the electrodes forms a hypochlorite solution which has the effect of killing off and preventing the growth of micro-organisms. There are many types and forms of electrolytic cells that may be used in the chlorination of pools and spas. Some are positioned in the plumbing associated with the filtration plant of the pool, while others are suspended or immersed directly into the body of water. For domestic swimming pools and spas, the electrolytic cell usually runs at a d.c. voltage of between 4 to 12 volts, enabling a current of between 5 to 40 amps to flow between the electrodes of the cell. The supply of the d.c. voltage is usually from a power pack that would include a step down transformer and a rectifier to step down the a.c. mains voltage to the d.c. voltage of between 4 and 12 volts.
One problem with electrolytic chlorination equipment is that, due to the generation of hydrogen gas, it is important that the electrolytic process does not continue when there is no flow of water through the cell. Thus, if the pump that is associated with the filtration system of a pool fails or is stopped for some reason, the flow of water ceases, which means that a small body of water is subjected to lengthy electrolysis in the cell. As the hydrogen gas produced by this extended electrolytic process is not being swept away by flowing water, given certain plumbing arrangements, a dangerous situation can result if the (potentially explosive) gas is able to accumulate in large "dead" spaces (like the filter tank). For this reason, power packs for electrolytic chlorinators usually include circuitry or componentry whose purpose is to interrupt the current to the cell in the event that the filter pump fails or stops. Circuitry or commonentry is also required to prevent overheating of the power pack in the event of current overload. The need for power packs, overload circuitry and means to interrupt current to the cell in the event of the filter pump failing adds considerably to the cost of electrolytic chlorination systems.
It is these problems that have brought about the present invention.